Copending application Ser. No. 09/886,288 and Ser. No. 09/886,289, both filed Jun. 22, 2001, both assigned to the assignee hereof, and both also hereby expressly incorporated by reference.
1. Technical Field of the Invention
The-present invention relates to the preparation/purification of water-soluble sulfonated organophosphorus compounds which are particularly well suited as two-phase catalysts for a variety of organic reactions.
2. Description of the Prior Art
Organophosphorus compounds are particularly important as ligands for transition metal elements to prepare catalytic systems for various organic reactions such as carbonylation, hydroformylation, hydrocyanation and the isomerization of olefinic compounds.
Such catalytic systems are generally employed in reactions involving a single phase and, thus, an occasionally complex step of separation and recovery of the catalyst is required.
In the early 1970s, water-soluble compounds able to form complexes with metal elements in the oxidation state of zero were proposed as catalysts. These water-soluble compounds generally belong to the family of organophosphorus compounds comprising at least one sulfonate group. Thus, F. Joes and M. T. Beck, in an article published in React. Kim. Catal. Letters, 2, 257 (1975), and Bawoski et al., in an article published in the review Nouv. J. Chem., 2, 137 (1978), describe a water-soluble monosulfonated triphenylphosphine which cannot be extracted using organic solvents.
The synthesis of these materials allowed the development of a novel method of catalysis referred to as two-phase catalysis. Specifically, the catalyst, i.e., transition metal elements complexed with water-soluble organophosphorus compounds, is present in an aqueous phase while the reagents are in an organic phase. Stirring and emulsification of the medium gives efficient catalysis. At the end of the reaction, the catalyst is recovered by simple separation by decantation of the two phases.
Rhxc3x4ne-Poulenc developed this technique for carrying out several important organic reactions such as the hydroformylation of olefins for the production of aldehydes, as described in FR-2,505,322 and FR-2,541,675. Another important application of this catalytic system, described, in particular, in FR-2,338,253 and FR-2,366,237, relates to the hydrocyanation reaction of olefins and the isomerization of the nitrites obtained, for example for the synthesis of adiponitrile, which is a major chemical intermediate for the manufacture of polyamide monomers.
Considerable research is nonetheless ongoing to improve the cost-effectiveness of these processes, in particular by increasing the cycle time and the lifetime of the catalytic system, as well as reducing the consumption of catalyst per quantity of adiponitrile produced.
Over the course of this research, degradation of the water-soluble sulfonated organophosphorus compounds has been observed.
Accordingly, a major object of the present invention is the provision of unique water-soluble sulfonated organophosphorus ligands which are resistant to degradation, and more stable two-phase catalytic systems comprised thereof.
Briefly, the present invention features carrying out organic reactions by two-phase catalysis, the media of reaction comprising an organic phase containing the reagents and the reaction products, an aqueous phase comprising a catalyst and a water-soluble sulfonated organophosphorus compound, wherein said water-soluble sulfonated organophosphorus compound has been purified via removal of contaminating sulfite compounds or radicals therefrom.
More particularly according to the present invention, in a preferred embodiment thereof, the sulfonated organophosphorus compounds thus purified have a weight concentration of sulfite of less than 100 ppm, preferably less than 50 ppm.
In another embodiment of this invention, the removal of sulfites is attained by converting same into sulfurous gas.
Exemplary organic reactions catalyzed via two-phase catalysis are hydroformylation, carbonylation, oxidation, isomerization and hydrocyanation reactions, in particular of unsaturated compounds.
In one preferred embodiment of the present invention, the hydrocyanation of organic compounds containing at least one ethylenic double bond is carried out to prepare nitrile compounds such as adiponitrile, for the synthesis of lactam, amino acid or amine monomers for the production of polyamides. This synthetic process, in particular, comprises a hydrocyanation of 3-pentenenitrile into adiponitrile, for which the catalyst comprising a sulfite-freed organophosphine in accordance with the invention as a component thereof is especially suitable.
Thus, in such an application, the lifetime of the catalyst can be greatly improved. This improvement is observed, in the case of the hydrocyanation of organic compounds comprising more than one ethylenic double bonds and in particular dienes, both for the hydrocyanation reaction of the first ethylenic bond and in that of the second ethylenic bond.
The process of the invention permits conducting the hydrocyanation of butadiene for the synthesis of adiponitrile with a catalyst based on water-soluble sulfonated organophosphorus ligands and on at least one metal element in oxidation state zero, with a consumption of catalyst per kg of adiponitrile produced which is markedly lower than that existing when using a catalyst or a ligand which has not been subjected to removal of sulfites.
In another preferred embodiment of the invention, removal of the sulfites contained in the water-soluble sulfonated organophosphorus compound is obtained by lowering the pH of the solution of organophosphorus compounds to a value of less than or equal to 4 and maintenance of such solution at a pH of less than or equal to 4 until a sulfite concentration in the solution of less than 100 ppm is attained.
Assay of the sulfite compounds in the solution is carried out, for example, by ionic chromatography.
The lowering of the pH of the solution can be accomplished by any suitable means. However, in another preferred embodiment of the invention, this lowering is accomplished by addition of a strong inorganic or organic acid in pure form or, more preferably, in solution.
The acidic solution can be a concentrated or dilute solution.
Exemplary acids which are suitable according to the present invention, representative are those acids having, for example, a pKa of less than or equal to 4, the corresponding anhydrides and more generally any compound which is chemically inert with respect to the organophosphorus compound and which can lower the pH of a solution.
Exemplary such acids are sulfuric acid, hydrochloric acid, trifluoroacetic acid, para-toluenesulfonic acid, perchloric acid and nitric acid.
Moreover, the solution of water-soluble sulfonated organophosphorus compounds is preferably an aqueous solution. However, solutions using water/alcohol mixtures as solvent are also suitable. The alcohol can be replaced with any water-miscible solvent.
In another embodiment of the invention, the solution is maintained at a pH of less than or equal to 4, at a temperature below 100xc2x0 C. and advantageously ranging from 40xc2x0 C. to 90xc2x0 C.
The sulfurous gas produced by converting the sulfites is, in one preferred embodiment of the invention, removed from the reaction medium by entrainment with a carrier fluid. This carrier fluid is preferably nonoxidizing. Thus, carrier fluids which are suitable for the invention are, for example, nitrogen, carbon dioxide, water vapor, rare or inert gases, and oxygen-depleted air.
The water-soluble sulfonated organophosphorus compounds which are suitable for treatment according to the process of the invention and which are useful as ligands in the processes of two-phase catalysis are generally the sulfonated organophosphorus compounds prepared via one or more sulfonation steps as described in the article published in J. Chem. Soc., pages 276-288 (1958) or in GB-1,066,261. These can also be prepared by reacting sodium p-chlorobenzenesulfonate with diphenylchlorophosphine, as described in the article by H. Schindlbauer, Monatsch. Chem., 96, pages 2051-2057 (1965).
Generally, these processes for synthesizing sulfonated organophosphorus compounds do not make it possible to obtain a compound which is free of sulfite compounds or radicals. Consequently, in order to avoid degradation of these compounds during their use as a catalyst or a ligand of a catalytic system, it is necessary according to the process of the invention to remove these sulfites at least partially.
Suitable water-soluble sulfonated phosphine compounds according to the invention include those described in FR-2,338,253 or in WO 97/12857 and EP 0,650,959.
Thus, suitable phosphines according to this invention have the following structural formula (I): 
in which Ar1, Ar2 and Ar3, which may be identical or different, are each an aryl radical; Y1, Y2 and Y3, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms, an alkoxy radical having from 1 to 4 carbon atoms, a halogen atom, a CN group, an NO2 group, an OH group, an NR1R2 radical, wherein R1 and R2, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms; M is an inorganic or organic cationic residue selected, such that the compound of formula (I) is soluble in water, from the group consisting of H+, cations derived from alkali metals or alkaline earth metals, N(R3R4R5R6)+, wherein R3, R4, R5 and R6, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms or a hydrogen atom, and other metal cations, the benzenesulfonic acid salts of which are soluble in water; m1, m2 and m3 which may be identical or different, are each an integer ranging from 0 to 5; and n1, n2 and n3, which may be identical or different, are each an integer ranging from 0 to 3, at least one of these being equal to or greater than 1.
Exemplary metals, the benzenesulfonic acid salts of which are soluble in water, include lead, zinc and tin.
By the expression xe2x80x9csoluble in waterxe2x80x9d is generally intended a compound soluble to at least 0.01 g per liter of water.
Preferred phosphines of formula (I) are those in which:
Ar1, Ar2 and Ar3 are phenyl radicals;
Y1, Y2 and Y3 are alkyl radicals having from 1 to 2 carbon atoms, or alkoxy radicals having from 1 to 2 carbon atoms;
M is a cation selected from the group consisting of H+, cations derived from Na, K, Ca and Ba, NH4+, and tetramethylammonium, tetraethylammonium, tetrapropylammonium and tetrabutylammonium cations;
m1, m2 and m3 are integers ranging from 0 to 3; and
n1, n2 and n3 are integers ranging from 0 to 3, at least one also being greater than 1.
The more particularly preferred phosphines are the sodium, potassium, calcium, barium, ammonium, tetramethylammonium and tetraethylammonium salts of mono(sulfophenyl)diphenylphosphine, di(sulfophenyl)phenylphosphine and tri(sulfophenyl)phosphine, in which the SO3 groups are preferably in the meta-position.
Exemplary phosphines of formula (I) according to the process of the invention are alkali metal or alkaline earth metal salts, ammonium salts, or quaternary ammonium salts of (3-sulfo-4-methylphenyl)di(4-methylphenyl)phosphine, (3-sulfo-4-methoxyphenyl)di(4-methoxyphenyl)phosphine, (3-sulfo-4-chlorophenyl)di(4-chlorophenyl)phosphine, di(3-sulfophenyl)phenylphosphine, di(4-sulfophenyl)phenylphosphine, di(3-sulfo-4-methylphenyl)(4-methylphenyl)phosphine, di(3-sulfo-4-methoxyphenyl)(4-methoxyphenyl)phosphine, di(3-sulfo-4-chlorophenyl)(4-chlorophenyl)phosphine, tri(3-sulfophenyl)phosphine, tri(4-sulfophenyl)phosphine, tri(3-sulfo-4-methylphenyl)phosphine, tri(3-sulfo-4-methoxyphenyl)phosphine, tri(3-sulfo-4-chlorophenyl)phosphine, (2-sulfo-4-methylphenyl)(3-sulfo-4-methylphenyl)(3,5-disulfo-4-methylphenyl)phosphine or (3-sulfophenyl)(3-sulfo-4-chlorophenyl)(3,5-disulfo-4-chlorophenyl)phosphine.
A mixture of these phosphines can of course be employed, in particular a mixture of mono-, di- and tri-meta-sulfonated phosphines.
Monodentate and bidentate phosphines having the following structural formulae (II) and (III) are also suitable according to the present invention: 
in which Ar1 and Ar2, which may be identical or different, are each aryl radicals or substituted such aryl radicals bearing one or more substituents, such as alkyl or alkoxy radicals having from 1 to 4 carbon atoms, halogen atoms, hydrophilic groups, such as xe2x80x94COOM, xe2x80x94SO3M or xe2x80x94PO3M, wherein M is an inorganic or organic cationic residue selected from among hydrogen, cations derived from alkali metals or alkaline earth metals, ammonium cations xe2x80x94N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, and other cations derived from metals, the arylcarboxylic acid, arylsulfonic acid or arylphosphonic acid salts of which are soluble in water, xe2x80x94N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, or xe2x80x94OH; Ar3 is a substituted aryl radical bearing one or more substituents, such as alkyl or alkoxy radicals having from 1 to 4 carbon atoms, halogen atoms, hydrophilic groups, such as xe2x80x94COOM or xe2x80x94PO3M, wherein M is an inorganic or organic cationic residue selected from among hydrogen, cations derived from alkali metals or alkaline earth metals, ammonium cations xe2x80x94N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, and other metal cations, the arylcarboxylic acid or arylphosphonic acid salts of which are soluble in water, N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, or xe2x80x94OH, with the proviso that at least one of the substituents of Ar3 is a hydrophilic group as defined above; a is 0 or 1; b is 0 or 1; c is an integer ranging from 0 to 3; D is an alkyl radical, a cycloalkyl radical or an alkyl or cycloalkyl radical substituted by one or more substituents, such as an alkoxy radical having from 1 to 4 carbon atoms, a halogen atom, a hydrophilic group, such as xe2x80x94COOM, xe2x80x94SO 3M or xe2x80x94PO3M, wherein M is an inorganic or organic cationic residue selected from among hydrogen, cations derived from alkali metals or alkaline earth metals, ammonium cations xe2x80x94N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, and other metal cations, the arylcarboxylic acid, arylsulfonic acid or arylphosphonic acid salts of which are soluble in water, xe2x80x94N(R)4, wherein the radicals R, which may be identical or different, are each a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, or xe2x80x94OH; d is an integer ranging from 0 to 3; and the sum (a+b+c+d) is equal to 3; and 
in which Ar1, Ar2 and D are as defined above for the formula (II); a, b, e, and f are each 0 or 1; d and g are each an integer ranging from 0 to 2; the sum (a+b+d) is equal to 2; the sum (e+f+g) is equal to 2; and L is a single valency bond or a divalent hydrocarbonaceous radical, such as an alkylene radical, a cycloalkylene radical, an arylene radical, or a radical deriving from a heterocycle comprising one or two oxygen, nitrogen or sulfur atoms in the ring, these various cyclic radicals being bonded directly to one of the phosphorus atoms or both phosphorus atoms or being bonded to one of the phosphorus atoms or to both via a linear or branched alkylene radical having from 1 to 4 carbon atoms, with the proviso that the ring or rings which are optionally moieties of the divalent radical L may comprise one or more substituents, such as an alkyl radical having from 1 to 4 carbon atoms.
Exemplary phosphines of structural formula (II) include tris(hydroxymethyl)phosphine, tris(2-hydroxyethyl)phosphine, tris(3-hydroxypropyl)phosphine, tris(2-carboxymethyl)phosphine, the sodium salt of tris(3-carboxyphenyl)phosphine, tris(3-carboxyethyl)phosphine, tris(4-trimethylammoniophenyl)phosphine iodide, the sodium salt of tris(2-phosphonoethyl)phosphine or bis(2-carboxyethyl)phenylphosphine.
And exemplary phosphines of structural formula (III) include the sodium salt of 2,2xe2x80x2-bis[di(sulfophenyl)phosphino]-1, 1xe2x80x2-binaphthyl, the sodium salt of 1,2-bis[di(sulfophenyl)phosphinomethyl]cyclobutane (CBDTS), 1,2-bis(dihydroxymethylphosphino)ethane, 1,3-bis(dihydroxymethylphosphino)propane, or the sodium salt of 2,2xe2x80x2-bis[di(sulfophenyl)phosphinomethyl] -1,1xe2x80x2-binaphthyl.
Certain of the water-soluble phosphines of formulae (I) to (III) are commercially available.
For the preparation of the others, reference is made to the general or specific processes for the synthesis of phosphines described in the general literature, such as Houben-Weyl, Methoden der organischen Chemie, xe2x80x9corganische Phosphor Verbindungenxe2x80x9d [Methods of Organic Chemistry, xe2x80x9cOrganic Phosphorus Compoundsxe2x80x9d], Part 1(1963).
Lastly, for the preparation of water-soluble derivatives which have not been described, starting from phosphines not comprising water-soluble substituents described above, one or more of these hydrophilic substituents are introduced. Thus, sulfonate groups, for example, may be introduced by the reaction of SO3 in sulfuric acid. Carboxylate, phosphonate and quaternary ammonium groups can likewise be introduced via the usual chemical techniques for this type of synthesis.
Other water-soluble sulfonated organophosphorus compounds which are suitable are the compounds BISBIS, NORBOS and BINAS described in the article by Boy Cornils and Emile G. Kuntz, published in Journal of Organometallic Chemistry, No. 502 (1995) pp. 177-186. Also suitable are the water-soluble furylphosphine compounds described in French patent application No. 98/06559, filed May 20, 1998, assigned to the assignee hereof.
As indicated above, the subject sulfite-freed organophosphorus compounds are particularly useful as components of catalysts comprising a transition metal element selected, for example, from the group consisting of nickel, cobalt, iron, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, zinc, cadmium and mercury in variable oxidation states.
It should be appreciated that, in these catalysts, generally, rhodium is in oxidation state (I), ruthenium is in oxidation state (II), platinum is in oxidation state (I), palladium is in oxidation state (II), osmium is in oxidation state (0), iridium is in oxidation state (0) and nickel is in oxidation state (0).
In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that same are intended only as illustrative and in nowise limitative.